Phthalocyanines are useful for preparation of paints, printing inks, catalysts, or electronic materials. In recent years, they have been extensively investigated for use in materials for electrophotographic photoreceptor, optical recording materials, and photoelectric conversion materials.
In connection with electrophotographic photoreceptor, a laser printer utilizing semiconductor laser has been increasingly demanded, and various photoconductive materials for the semiconductor laser have been proposed. In particular, a large number of phthalocyanine compounds as photoconductive materials have been reported.
It is known that a phthalocyanine compound generally exhibits varied crystal forms depending on a method of preparation and a method of processing thereof, and that this difference in crystal form exerts great influences on photoelectric conversion characteristics of the phthalocyanine compound.
In connection with the crystal form of the phthalocyanine compound, in the case of copper phthalocyanine, for example, as well as a .beta.-type crystal form which is of the stabilized system, .alpha.-, .pi.-, .chi.-, .rho.-, .gamma.-, .delta.-, and like crystal forms are known. It is also known that the above crystal forms can transfer from one another upon application of mechanical stress, sulfuric acid treatment, organic solvent treatment, or heat treatment (see, for example, U.S. Pat. Nos. 2,770,629, 3,160,635, 3,708,292, and 3,357,989). In addition, JP-A-50-38543 (the term "JP-A" as used herein means an "unexamined Japanese patent application") describes a relation between the crystal form of copper phthalocyanine and electrophotographic characteristics.
In connection with the crystal form of oxytitanium phthalocyanine, and electrophotographic characteristics, JP-A-62-67094 describes the .beta.-type crystal form which is of the stabilized system, and JP-A-61-2170506 describes the .alpha.-type crystal form obtained by the acid pesting method or the solvent treatment. In addition, JP-A-63-366, 64-17066. 1-153757, and 63-20365, for example, describe crystal forms other than the .alpha.- and .beta.-crystal forms.
It is generally well known that doping of impurities in organic or inorganic semiconductors results in great changes of electric characteristics thereof.
N.R. Armstrong et al report doping of I.sub.2, and changes of photoconductive characteristics are due to adsorption of O.sub.2, H.sub.2 O, etc., in an oxytitaniumphthalocyanine vacuum deposited film (AIP Conf. Proc., 167 (1988), Proc. Electrochem. Soc., 88 14, 267 (1987), and J. Phys. Chem., Vol. 91, 5646 (1987)).
The aforementioned conventional oxytitanium phthalocyanine compounds, however, have poor crystallinity in solvents and thus cannot hold their crystal forms for a long time in the state after being dispersed and coated. Moreover, when used as photosensitive materials, they are not yet satisfactory in light sensitivity and durability.